Fixed plot height question

I've tried many things, so it's time to call on the gurus.  I'm  
trying to make a plot that will conform to the width of the plot  
device but have a fixed height (say one inch regardless of the plot  
device height setting -- unless obviously it's less than the plot  
device).

Is this possible?

Additionally, I'd like to be able to plot something immediately after  
this plot and have it right below.  Would this require a par(mfrow=c 
()) command? Can anyone help?

Thanks.